In thermal printing, it is generally well known to render images by heating and pressing one or more donor materials such as a dye, colorant or other coating against a receiver medium. The donor materials are provided in sized donor patches on a movable web known as a donor ribbon. The donor patches are organized on the ribbon into donor patch sets, each donor patch set contains all of the donor patches that are to be used to record an image on the receiver medium. For full color images, multiple colored dye sets can be used, such as yellow, magenta and cyan donor dye patches. Arrangements of other color patches can be used in like fashion within a donor patch set. Additionally, each donor set can include an overcoat or sealant layer.
It will be appreciated from this that the size of the donor patches defines the full size image that can be printed using a conventional thermal printer. To provide flexibility of use, many thermal printers are capable of printing relatively large images such as 6″×8″ images. While prints of this size are highly desirable for many uses, it can be challenging to use and store images printed at this size. Accordingly, consumers often request that such printers render images at a fraction of the full size image, such as images printed at the wallet size, 3″×5″ size or 4″×6″ size. Images at these sizes are more easily used and stored and exhausts only a fraction of the donor material from a donor patch set leaving a fraction donor patch set.
Unfortunately, the printers of the prior art are not adapted to use the remaining donor material from a fractionally used donor patch set for printing other images. Instead, it is conventionally known to have a thermal printer advance to the next complete donor set after printing a fractional size image so that the thermal printer is prepared to print any size image when the next printing order is received. It will be appreciated that this results in inefficient use of the donor material causing increased printing expense. What is needed therefore is a thermal printer control system and a method that enables more efficient use of donor material.